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Topic: Couple of Questions on LilyPad Arduino (Read 6621 times) previous topic - next topic

adood84

Apr 05, 2008, 09:12 am Last Edit: Apr 05, 2008, 09:37 am by adood84 Reason: 1
Hello, I'm new to this forum so I'm sorry if this is posted in the wrong sections :)

Basically I want to make a present box that would have a count down to a certain date , when that date reaches the lock would unlock and the present could be open. A count down would be shown on small screen or something of that type.

I was thinking that LilyPad Arduino would fit the job because of its low power needs , and it's small size. The Basic idea in my head is that maybe I could hack into a counter watch of some sort and set the countdown and take the alarm signal and route it the arduino to  interrupt it then it will unlock the lock.

Do you think this is doable with the LilyPad ? is the LilyPad the right choice? and could have this working on a battery for 1 or 2 months or so without the need to change the battery for the LilyPad? as I'm thinking of getting this kit http://www.sparkfun.com/commerce/product_info.php?products_id=8617#




thanks for the help :)

leahb

#1
Apr 05, 2008, 04:53 pm Last Edit: Apr 05, 2008, 04:55 pm by leahb Reason: 1
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Do you think this is doable with the LilyPad ? is the LilyPad the right choice?

The LilyPad uses the AVR's internal oscillator for timing, so the time measurements on the LilyPad aren't going to be as accurate as those on the other Arduinos, which have external crystals.  I'm not sure how long it would take the LilyPad to get off by a day on timing...  

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and could have this working on a battery for 1 or 2 months or so without the need to change the battery for the LilyPad?

This is going to be hard to do with any Arduino and reasonably sized battery.  To do this properly you'd want to use a raw AVR (or PIC or whatever) chip & use its sleep/power saving modes...  Just powering the LilyPad takes ~5-10 mA of current.  Batteries are rated for mA hours: so, if a battery is rated 1000 mA hours, that means it'll power the LilyPad for at most 200 hours...  The other Arduinos take ~ twice as much current to run as the LilyPad since their clock speed is twice as fast.

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as I'm thinking of getting this kit http://www.sparkfun.com/commerce/product_info.php?products_id=8617#

You probably don't need everything in this kit.  You probably don't need the thread, light sensor or RGB LED.  So you're better off just getting the components you need: LilyPad, power supply & USB Link...


Oracle

Just a couple of comments:

Make sure you design the mechanical part of the box so that it fails unlocked or there's some other way to unlock it.  You don't want the box permanently locked if the battery dies or there's a glitch in the software.

For precise timing over a few months you need a crystal.  The internal oscillator is accurate to about 1% or 12 minutes a day, or you can be out by a full day in 4 months.  You may also consider a real-time clock chip.  It won't make it more accurate, but it make it easier to keep track of time and gives you a long term battery back-up for the clock time.


follower

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and could have this working on a battery for 1 or 2 months or so without the need to change the battery for the LilyPad?

As an initial data point, here's some Arduino battery life research results.

--Phil.

adood84

#4
Apr 05, 2008, 06:49 pm Last Edit: Apr 05, 2008, 07:06 pm by adood84 Reason: 1
So I guess I should ditch the LilyPad idea then? or can I use the LolyPad with the real time chip? because I need something compact to package it inside the a smallish box. Also it would seem that it would be a good idea to use a constant power supply? from an adapter or something.

from the quick search I did I found this real-time chip

http://www.emesystems.com/pdfs/parts/DS1307.pdf

I haven't looked at the lock part of the design yet...

How easy do you guys think this project is going to be ?

Also any links to more info about Arduino would be much appreciated :)

adood84

OK after a lot of thinking the time requirement has been reduced from 2 months 6 hours which according to the above is doable with a LilyPad and a normal AAA battery , correct? and its going to be kind of accurate for that time.

John_Ryan

#6
Apr 05, 2008, 08:43 pm Last Edit: Apr 05, 2008, 09:08 pm by John_Ryan Reason: 1
I found these the other day, this will get you close to 2000 hours - almost what you need but they are not cheap :)

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3718

And here's an i2c real time clock, SDA and SCL will connect to A4 and A5 on the lilypad.

http://www.futurlec.com/Mini_PCF8583.shtml

Cheap too.

Oracle

#7
Apr 06, 2008, 08:12 am Last Edit: Apr 06, 2008, 08:13 am by Oracle Reason: 1
Aren't plain old alkaline D batteries in the 30 Ah range? 3 of them in series will get you well into operating range of the '168.  If the lilypad takes 10mA, you should get 3000 hours or 125 days of run time for about $5.

Add the DS1307 with a crystal and the timing should also be accurate enough.  Comparable to a digital wristwatch.  So you might be out a minute or two over a couple of months.

adood84

#8
Apr 06, 2008, 10:01 am Last Edit: Apr 06, 2008, 10:02 am by adood84 Reason: 1
Can I use the LilyPad and the DS1307 and an LCD screen for 6 hours ? are there enough pins to connect an LCD and the real time chip? because teh basic idea is now are in these steps :

1- Count down for 6 hours /Display the countdown on an LCD
2- when count down is done display a message on the LCD and Unlock the lock .


Sorry for all the newbie questions :)

Oracle

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Can I use the LilyPad and the DS1307 and an LCD screen for 6 hours ? are there enough pins to connect an LCD and the real time chip? because teh basic idea is now are in these steps :

1- Count down for 6 hours /Display the countdown on an LCD
2- when count down is done display a message on the LCD and Unlock the lock .


Sorry for all the newbie questions :)


There should be no problems doing this.  The DS1307 takes 2 pins on your Arduino.

How is the lock part going to work?  I'd still be worried about a failure permanently locking the box.

leahb

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OK after a lot of thinking the time requirement has been reduced from 2 months 6 hours which according to the above is doable with a LilyPad and a normal AAA battery , correct? and its going to be kind of accurate for that time.


Just one more thing to keep in mind.  When you use a AAA battery in the lilypad power supply, you need to factor the voltage step-up into your thinking.  Since the LilyPad power supply outputs 5V (versus the 1.5 the AAA provides), you should ~ divide the AAA mA hour rating by 4 to get a good estimate of how long it will last (4*1.5 = 6V).  If it's rated 1000mAh, it'll only supply 250 mAh when you use it in the lilypad power supply...

Oracle

#11
Apr 06, 2008, 10:22 pm Last Edit: Apr 06, 2008, 10:23 pm by Oracle Reason: 1
Quote
Just one more thing to keep in mind.  When you use a AAA battery in the lilypad power supply, you need to factor the voltage step-up into your thinking.  Since the LilyPad power supply outputs 5V (versus the 1.5 the AAA provides), you should ~ divide the AAA mA hour rating by 4 to get a good estimate of how long it will last (4*1.5 = 6V).  If it's rated 1000mAh, it'll only supply 250 mAh when you use it in the lilypad power supply...


That will drive the Lilypad and LCD for plenty of time for his new 6 hour estimate, but I'm still wondering about the lock.  A solenoid will use a lot of current.  The battery might be weak enough after 6 hours that it can't handle the current.  A servo motor actuating a lock could work but adds a lot of hardware for the driver and I hope he's not powering any additional stuff for that 6 hours.

We really have no info on the lock.

adood84

#12
Apr 07, 2008, 09:08 am Last Edit: Apr 07, 2008, 09:08 am by adood84 Reason: 1
Quote
Quote
Just one more thing to keep in mind.  When you use a AAA battery in the lilypad power supply, you need to factor the voltage step-up into your thinking.  Since the LilyPad power supply outputs 5V (versus the 1.5 the AAA provides), you should ~ divide the AAA mA hour rating by 4 to get a good estimate of how long it will last (4*1.5 = 6V).  If it's rated 1000mAh, it'll only supply 250 mAh when you use it in the lilypad power supply...


That will drive the Lilypad and LCD for plenty of time for his new 6 hour estimate, but I'm still wondering about the lock any help in this area would be much appreciated .  A solenoid will use a lot of current.  The battery might be weak enough after 6 hours that it can't handle the current.  A servo motor actuating a lock could work but adds a lot of hardware for the driver and I hope he's not powering any additional stuff for that 6 hours.

We really have no info on the lock.



The lock is something I still haven't figured out , any ideas about what type of locks are out there? I tried googling electric locks but all I get some really big ones . There will be nothing to power other than the LCD , the LilyPad, the Real-Time chip and the lock ... the lock is going to be unlocked once and thats it .

What I'm thinking is that the lock would be locked without the need for power , once it receives a signal the lock would open and stay open without the need for power (not sure if such things exists though). An option is to have a separate power supply for the lock and use the LilyPad to signle an electric switch (transistor??) to let the power through to the lock. No I need to find me a lock lol

John_Ryan

If you do find any miniature electro magnetic / electro mechanical / or even small electric strike locks, be sure to post back.

You could latch the door so it springs open when the solenoid releases it, that way you'd only need momentary power if it's a one off event.

adood84

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If you do find any miniature electro magnetic / electro mechanical / or even small electric strike locks, be sure to post back.

You could latch the door so it springs open when the solenoid releases it, that way you'd only need momentary power if it's a one off event.



thats exactly what I want it to do , cause I can't be sure if the person would be there when it unlocks , it could unlock while the person isn't there and they could come back later to open it .

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